1. Field of the Invention:
The present invention relates to a webbing retractor for use in a seatbelt system designed to protect an occupant of a vehicle when an emergency situation occurs. More particularly, the present invention pertains to a webbing retractor which is arranged such as to protect the occupant from any discomfort caused by the pressure of the webbing of the seatbelt system.
2. Description of the Prior Art:
In seatbelt systems, a webbing is generally wound up onto a take-up shaft by means of the biasing force of a spiral spring.
Since the webbing needs to be fully wound up after the occupant releases the seatbelt, the spiral spring is required to have a relatively large biasing force.
Accordingly, it is necessary for the occupant to pull on the webbing with considerable force when unwinding the webbing in order to fasten it. In addition, the occupant may experience discomfort from the pressure of the webbing when he moves in the seat while driving with the webbing fastened.
In order to overcome the above-described disadvantages, one type of webbing retractor has previously been proposed in which the outer end of a spiral spring is turned by employing a motor so that the webbing wind-up force can be adjusted (see, e.g., Japanese Utility Model Application No. 75129/1983).
However, this webbing retractor, in which the webbing wind-up force is made adjustable by the use of a motor, needs a webbing tension detector in order to adjust the webbing tension in accordance with the condition of the webbing, which changes depending on whether, for example, the occupant has the webbing fastened or not. In consequence, the structure and control of this type of conventional webbing retactor are overly complicated.